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In the last twenty years, remarkable advances in nanosciences and nanotechnology have given an impulse to the design of heterogeneous catalysts. Bell emphasized in 2003 the role of nanoparticle size in catalyst performance, [1] and Schlögl and Abd Hamid [2] proposed in 2004 that the synthesis of nanosized catalysts may require multidimensional structural control. Glow-discharge (luminous) plasma is obtained by applying a potential difference between two electrodes placed in a gas. The plasma provides energy for decomposition of metal precursors. Several active catalysts have been developed [3][4][5][6] by using glow discharge. The glow-discharge activation process is simple, quick, audio-visual, and easy to control. It does not require the high temperatures and significant amounts of compressed gases which are typically used in conventional catalyst pretreatments.The increasing interest in Fischer-Tropsch (FT) synthesis has been due to the growing demand for clean fuels and utilization of abundant natural gas, coal, and biomass-derived synthesis gas. [7,8] Cobalt catalysts are preferred for FT synthesis due to their high productivity, high selectivity for heavy hydrocarbons, high stability, and low activity in the water-gas shift reaction. [7,8] The catalytic performance of cobalt catalysts in FT synthesis appears to be strongly affected by the size of the cobalt metal particles. [7][8][9][10][11] Conventional cobalt FT catalysts are prepared by aqueous impregnation of supports (silica, alumina, titania, etc.) with solutions of cobalt salts. After decomposition of the supported cobalt salts by calcination in an oxidizing atmosphere, the catalysts are reduced in hydrogen to generate cobalt metal sites.The present work focuses on the effects of pretreatment with glow-discharge plasma on cobalt dispersion and reducibility in alumina-supported catalysts and their performance in FT synthesis. Details of catalyst preparation are given in the Experimental Section. Cobalt and platinum contents in catalysts were 15 wt % and 0

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The nature of cobalt species in the catalysts supported by multi-wall carbon nanotubes and their catalytic performance in Fischer-Tropsch synthesis were investigated using nitrogen adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy, in situ magnetic method, X-ray absorption and temperature programmed reduction. The catalysts were prepared by incipient wetness impregnation using solutions of cobalt nitrate assisted by sonochemical process followed by calcination in nitrogen. The characterization techniques uncovered that acid pretreatment oxidized the carbon nanotube surface and removed impurities. Small cobalt oxide particles of 8-10 nm diameter and irregular shape anchored to the outer surface of carbon nanotubes were detected in the calcined samples by several characterization techniques. The catalysts displayed high cobalt reducibility, which was slightly affected by the pretreatment with nitric acid and nanotube outer diameter. Cobalt catalysts supported on carbon nanotubes exhibited high catalytic activity in Fischer-Tropsch synthesis. Pretreatment with nitric acid leads to a 25% increase in hydrocarbon yield, while carbon nanotube diameter does not seem to significantly affect the Fischer-Tropsch performance of the resulting catalysts.